The use of hybrid inflators for the inflation of air bags in automobiles is well known. Typically, a hybrid inflator includes a rupturable burst disk which releases a flow of gas from a pressure vessel in which the gas is stored to an airbag for inflation thereof. Rupture of the burst disk is responsive to a sensed vehicle condition such as a collision.
In certain hybrid inflators, an igniter assembly is provided which, when actuated, ignites a body of solid pyrotechnic material. The ignited pyrotechnic material heats and pressurizes a stored inflator gas. The heated and pressurized stored inflator gas is then released for airbag inflation by rupture of the burst disk.
One of the drawbacks of these types of hybrid inflators is the generation of solid particulates in the effluent gas which is derived from the solid propellant. The solid particulates can adversely affect the inflator performance by burning a hole in the airbag during its inflation. One reason for the excessive levels of solid particulates is that the solid propellant used in prior art inflators uses a combination of combustible and non-combustible material. When a solid propellant is ignited, only the combustible material burns and generates gaseous products of combustion. The non-combustible materials or solid particulates are carried along in the gases during the inflator operation. The use of solid propellant in inflators also increases the size and weight of inflators due to the use of non-combustible material in the solid propellant. Solid propellant-using prior art inflators also fail to provide flexibility in inflator performance since the solid propellants are not readily adaptable to different inflator performance needs.
In view of the drawbacks of these prior art hybrid inflators, a need has developed to provide an improved hybrid inflator which reduces solid particulate levels in the effluent gas when inflating airbags and also provides increased flexibility in inflator performance. In addition, a need has developed to provide inflator designs which are lighter in weight, simpler in design and lower in manufacturing costs.
In response to these needs, the present invention provides a hybrid inflator which utilizes a liquid fuel in combination with a solid propellant and a compressed inflator gas.